How to Do a Newline in Output

How to do a newline in output

Use "\n" instead of '\n'

Most efficient way to output a newline

The answer to this question is really "it depends".

In isolation - if all you're measuring is the performance of writing a '\n' character to the standard output device, not tweaking the device, not changing what buffering occurs - then it will be hard to beat options like

 putchar('\n');
 fputchar('\n', stdout);

 std::cout.put('\n');

The problem is that this doesn't achieve much - all it does (assuming the output is to a screen or visible application window) is move the cursor down the screen, and move previous output up. Not exactly a entertaining or otherwise valuable experience for a user of your program. So you won't do this in isolation.

But what comes into play to affect performance (however you measure that) if we don't output newlines in isolation? Let's see;

• Output of stdout (or std::cout) is buffered by default. For the output to be visible, options include turning off buffering or for the code to periodically flush the buffer. It is also possible to use stderr (or std::cerr) since that is not buffered by default - assuming stderr is also directed to the console, and output to it has the same performance characteristics as stdout.
• stdout and std::cout are formally synchronised by default (e.g. look up std::ios_base::sync_with_stdio) to allow mixing of output to stdout and std::cout (same goes for stderr and std::cerr)
• If your code outputs more than a set of newline characters, there is the processing (accessing or reading data that the output is based on, by whatever means) to produce those other outputs, the handling of those by output functions, etc.
• There are different measures of performance, and therefore different means of improving efficiency based on each one. For example, there might be CPU cycles, total time for output to appear on the console, memory usage, etc etc
• The console might be a physical screen, it might be a window created by the application (e.g. hosted in X, windows). Performance will be affected by choice of hardware, implementation of windowing/GUI subsystems, the operating system, etc etc.

The above is just a selection, but there are numerous factors that determine what might be considered more or less performance.

How do I specify new lines in a string in order to write multiple lines to a file?

It depends on how correct you want to be. \n will usually do the job. If you really want to get it right, you look up the newline character in the os package. (It's actually called linesep.)

Note: when writing to files using the Python API, do not use the os.linesep. Just use \n; Python automatically translates that to the proper newline character for your platform.

Echo newline in Bash prints literal \n

Use printf instead:

printf "hello\nworld\n"

printf behaves more consistently across different environments than echo.

How can I echo a newline in a batch file?

echo hello & echo.world

This means you could define & echo. as a constant for a newline \n.

How to use newline '\n' in f-string to format output in Python 3.6?

You can't. Backslashes cannot appear inside the curly braces {}; doing so results in a SyntaxError:

>>> f'{\}'
SyntaxError: f-string expression part cannot include a backslash

This is specified in the PEP for f-strings:

Backslashes may not appear inside the expression portions of f-strings, [...]

One option is assinging '\n' to a name and then .join on that inside the f-string; that is, without using a literal:

names = ['Adam', 'Bob', 'Cyril']
nl = '\n'
text = f"Winners are:{nl}{nl.join(names)}"
print(text)

Results in:

Winners are:
Adam
Bob
Cyril

Another option, as specified by @wim, is to use chr(10) to get \n returned and then join there. f"Winners are:\n{chr(10).join(names)}"

Yet another, of course, is to '\n'.join beforehand and then add the name accordingly:

n = "\n".join(names)
text = f"Winners are:\n{n}"

which results in the same output.

Note:

This is one of the small differences between f-strings and str.format. In the latter, you can always use punctuation granted that a corresponding wacky dict is unpacked that contains those keys:

>>> "{\\} {*}".format(**{"\\": 'Hello', "*": 'World!'})
"Hello World!"

_{(Please don't do this.)}

In the former, punctuation isn't allowed because you can't have identifiers that use them.

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Aside: I would definitely opt for print or format, as the other answers suggest as an alternative. The options I've given only apply if you must for some reason use f-strings.

Just because something is new, doesn't mean you should try and do everything with it ;-)

Extra newline output when using print() in Python

When reading file with this idiom:

with open("line.txt") as f:
    for line in f:

The line comes with a \n character at the end.

Try this:

with open("line.txt") as f:
    for line in f:
        line = line.strip()  # Removes the "\n" character
        for word in line.split():
            if word == 'Way':
                line = line.replace("Way", "Street")
        print(line, end="\n") # Puts back the "\n" character.

Or you can use print(line, end=""). By default, print() ends with a \n char, you can specify the the end="" to be to avoid the extra newline with the line isn't striped when reading, i.e.

with open("line.txt") as f:
    for line in f:
        for word in line.split():
            if word == 'Way':
                line = line.replace("Way", "Street")
        print(line, end="")

How to print a linebreak in a python function?

You have your slash backwards, it should be "\n"

How do I create a new line in Javascript?

Use the \n for a newline character.

document.write("\n");

You can also have more than one:

document.write("\n\n\n"); // 3 new lines!  My oh my!

However, if this is rendering to HTML, you will want to use the HTML tag for a newline:

document.write("<br>");

The string Hello\n\nTest in your source will look like this:

Hello!

Test

The string Hello<br><br>Test will look like this in HTML source:

Hello<br><br>Test

The HTML one will render as line breaks for the person viewing the page, the \n just drops the text to the next line in the source (if it's on an HTML page).

Starting a new line of text in C

You can use the '\n' escape sequence to represent a newline (i.e. line-break) in your printf calls. Since your IDE/code editor most likely uses a monospaced font it should be pretty easy to align the * characters properly:

printf ("******************************\n");    
printf ("** Welcome to C Programming **\n");    
printf ("******************************\n");

Or, if you wanted to put the whole thing in a single printf call, you can use the \ character followed by a newline in a string literal to break the representation of the string in your editor over multiple lines:

printf (
"******************************\n \
** Welcome to C Programming **\n \
******************************\n"
);

Or even:

printf ("******************************\n" 
        "** Welcome to C Programming **\n"
        "******************************\n");

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